Networks or buses are already known in which the physical connection between stations is provided by a serial line for serial transmission with random access and collision detection, and they are referred to as "CSMA/CD" (Carrier-Sense Multiple-Access/Collision-Detection) networks or buses. Such networks control allocation of the serial line by arbitration means designed to resolve conflicts between a plurality of stations requesting the line substantially at the same instant. Thus, the "Ethernet" CSMA/CD network uses a common line both for line arbitration and for conveying data.
That system and similar systems nevertheless suffer from the major drawback of losing time in the event of a collision between two stations that have both attempted to send data at the same moment. It is then necessary to discard frames that have been disturbed by the collision and to allocate the network to one of the stations before data interchange can be restarted, and then all of the discarded frames must be retransmitted. The overall bit rate at which digital data is effectively interchanged thus drops sharply when conflicts of access are numerous.
An object of the present invention is to control allocation of the serial line in time that is masked from the interchanges of data that are performed on said line, thereby avoiding the need, in the event of a collision, to discard interfering frames or to repeat an interchange that has been disturbed.
The invention also seeks to coordinate in simple manner the transfer of data and the arbitration process, and to guarantee that the serial line is allocated quickly to all stations requesting it.